Method of and means for positioning apparatus in well casings



l b b U SLAHCHROOM Oct. 15, 1963 H J, DOAK 3,106,960

METHOD OF AND MEANS FOR POSITIONING APPARATUS IN WELL CASINGS Filed Jan.8*, 1960 5 Sheets-Sheet l FVG. 2

INVENTOR. Hou/Ago cx .oo/ne,

oct. 15, 1963 H. J. DOAK METHOD OF AND MEANS FOR POSITIONING APPARATUSIN WELL CASINGS Filed Jan. 8, 1960 3 Sheets-Sheet 2 FIG. 7.

- CoElzeLA'rwN CURVE- CuEEL/FEIELN 52 f 45 aoco 46 JNVENTOR.

How/:e0 d 004e,

/z'mmm 29m/LM W" A TTOBA/E YS.

3,106,960 METHOD OF' AND MEANS FOR POSITIONING APPARATUS IN WELL CASINGSFiled Jan. 8, 1960 H. J. DOAK Oct. 15, 1963 5 Sheets-Sheet .I5

United States Patent O 3 106,960 METHOD OF AND IEANS FOR POSITIONINGAPPARATUS IN WELL CASINGS Howard J. Doak, 3311 E. 45th St., Tulsa, Okla.Filed Jan. 8, 1960, Ser. No. 1,219 6 Claims. (Cl. 166-66) This inventionhas general reference to the location of apparatus and equipment ofvarious kinds, in cased bore holes. More specifically, the invention hasreference to a method of `and means for positioning said apparatus inoil well casings, during wire line operations wherein it is necessary tolower a particular piece of equipment, on a wire line, to apredetermined depth with a minimal loss of accuracy in the determinationof the exact position at which the apparatus is to be placed in use.

In wire line operations, such as perforating the well casing, settingcement retainers, bridge plugs, and permanent packers, the normalprocedure is to lower the perforating gun or other tool into the hole,with a collar locator attached. The collar locator is used to identifycollars which have previously been logged on a correlation-collar 10g.

Presumably, one might expect to be able to lower the tool to the exactdepth desired, merely by noting the response on the conventional collarlog, during the descent of the tool with its attached collar locator.However, difculties are encountered, owing to the fact that deviationsoccur in the wire line, ias the operation progresses, due to changes intension, weight, temperature, etc. These deviations can have greatsignificance, and if not properly calculated and compensated for, caneasily result in animproper positioning of the apparatus. In wells ofgreat depth, an oil-producing stratum may be no more than a few feet inthickness, and thus it will be seen that it is exceedingly important tolocate a perforating tool with complete accuracy, so that perforation ofthe casing will occur at the exact location of the producing stratum.The same requirement for complete accuracy exists, as will be readilyappreciated, in connection with various other types of wire lineoperations.

It is often difficult, in this regard, to identify a particular collar,without lowering the perforating gun or other tool fully to the bottomof the casing for the purpose of checking or calculating accuracy of thewire line. This, of course, is a time-consuming operation, and even so,is not fully productive of complete accuracy. The use of casing collarsas markers, that is, as datum points, is obviously a secondary functionof the casing collars, since their primary function is to join togetheradjacent, abutting lengths of the pipe of which the casing is formed.Thus, the spacing of the markers constituted by the casing collars isdetermined by the lengths of the pipe sections, and is not necessarilyan optimum spacing of casing markers employed during the positioning ofapparatus in wire line operations. In other words, one is required touse as a marking means or datum, a piece of equipment, the primaryfunction of which is something other than the provision of a referencepoint.

Normal procedure, during oil well completion operations, is to prepare acorrelation log. Graphically depicted upon a log of this type is atleast one correlation curve, showing the various formations or stratathrough the use of an undulant line, the deviations of which indicatethe different formations. The correlation log, further, includes acollar log, immediately adjacent :the correlation curve, the collar logconstituting a diagrammatic representation of the oil well, showing theposition of the casing collars or couplings, and quite possibly othercomponents of the casing, including float collars, guide shoes, stagecementing collars, etc. i

3,106,960 Patented Oct. 15, 1963 ICC The correlation log is preparedthrough the use of existing equipment, and thus, conventional loggingtools, available to the oil industry, are regularly used to identifydepth relationships with adjacent formations in wells. Said loggingequipment, as already known to the industry, further includes collarlocators, which are adapted to transmit signals to the surface, as theymove past casing collars or couplings.

Thus, after a well casing has been installed, a correlation log of thetype 'described above is prepared, and is thereafter used forpositioning apparatus during wire line operations, such as perforatingthe casing, setting cement retainers, etc. In the perforation of thecasing, for example, a perforating gun must be lowered by means of awire line to the producing formation, which might be only a few feetthick and which will likely be at a great depth. On proper positioningof the perforating gun, said gun is triggered from the ground level. Thegun thus lires projectiles or jets through the casing, into theproducing formation, to complete the operation of perforating the wellcasing. j i

The general practice, during an operation of this type, is to lower theperforating gun or other tool into the hole with a collar locatorattached. As the tool moves downwardly, the collar locator is used toidentify collars which have previously been logged on theabove-mentioned collar log. Ultimately, one of the collars becomes areference point, with respect to the producing formation or other levelof the well at which the tool is to be positioned.

It is often difficult, however, to identify a particular collar withoutlowering the gun or other tool fully to the bottom of the well -to checkthe accuracy of the wire line. This, as will be readily understood, is atime-consuming process, and even so, is productive of inaccuracies.

The locating of the gun or other apparatus, as noted previously, must beaccomplished with exceedingly high accuracy, since the thickness of theoil-bearing sands may sometimes be no greater than a few feet. Notinfrequently, the tolerance for work of this type cannot be permitted toexceed one or two feet in a total depth of perhaps 10,000 to 12,000feet. Precision positioning of the apparatus, as will be appreciated,thus becomes a task of great dilliculty.

Complications and uncertainties arise in the positioning process, sincethe common practice is to determine depths in the bore hole from drillpipe measurements, as distinguished from depth measurements made inwireline operations, wherein the measurements are made by calculatingdisplacements of the elastic suspension cable supporting the apparatus.

The factor of making corrections on account of the elasticity of thesuspension cable produces the complications and uncertaintieshereinbefore referred to. The extent to which the suspension cablestretches bears a relationship to the load -applied thereto, and isrelated, further, to the amount of cable payed out. Accordingly, whenany device, such as a perforating tool, is lowered into a Well in wireline operations, corrections must be made in footage tabulations, inaccordance with comparatively complicated, theoretical factors ofdeviation.

To overcome the difficulties discussed above, it has been heretoforeproposed to provide marking means, other than the conventional casingcomponents. For example, it has been proposed to fire a projectile ofradioactive or magnetic material,` directly into a formation at apredetermined depth, whereby to establish a reference point on which allsubsequent measurements may be based. It has also been proposed to formopenings directly in the well casing, which openings are then pluggedwith magnetic material. Still further, it has been proposed to attach aniron shoe or the like to a casing, at a particular point along thelength thereof, which shoe will provide a reaction at the ground surfacewhen a suitable sensing instrument or detecting tool moves to a positlonabreast of the same.

The -arrangements heretofore devised have not gained widespread success,and this may be due to the fact that they have had on-ly single-purposeor at least highly limited use, in respect to positioning apparatus ofvarious types. For instance, the special marking means lheretoforedevice have been utilized for the purpose olf aiding in the positioningof perforating guns, but are not usable, lany more than the casingcollars themselves, in the eilicient, accurate positioning of othertypes of apparatus that might have to be located at a substantialdistance from the producing formation. Further, in an instance in whichthe marker is applied by means of a piece of equipment lowered into .thewell casing, it may readily happen that the marker itself will beinaccurately positioned, since its accurate llocation depends upon thecorrespondingly exact positioning of the equipment which is lowered intothe casing for the purpose of firing or otherwise applying the marker.

Alternatively, when the marker is applied to the casing, it isundesirable to require re-design of the casing itself for the purpose ofreceiving a marking insert, in a recess or opening specially formed inthe wall of the casing.

To overcome these disadvantages, it is an important object of thepresent invention to provide casing markers that can be produced inquantity, at relatively low cost, and applied 4to a well casing at anyselected locations along t'he length of a casing section, includinglocations between the casing collars or couplings, all without anyre-designing, drilling, or other modification of the conventional casingconstruction. Another object of importance is to provide a casing markerwhich will be characterized by the swittness and ease with which it canbe slipped onto a casing, secured thereto at a selected point, :andthereafter permanently retained in posi-tion, dur'ing the conventionalprocedure of running a pipe string into the bore hole.

A further object is to provide a casing marker which will be be sodesigned as to insure to the maximum extent against any interferencewith normal casing installation, well completion, or pumping operationsfollowing perforation of the casing.

Another object is to speed up, to a marked degree, any wire lineoperations, including not only perforating, but also other operationssuch yas the setting of bridge plugs, through the provision of aplurality of the casing markers, regularly spaced along the entirelength of the casing and logged at ground level in vthe same manner asthe conventional casing collars are logged. Itis proposed, in thisregard, to accomplish the speeding up of the wire line operationsthrough the provision of the series of spaced markers, any one of whichcan be swiftly located in relation to an adjacent formation, to providea datum point, without the necessity of lowering the apparatus fully tothe bottom of the well for the purpose of checking the wire lineaccuracy.

A further object is 'to increase accuracy of positioning of apparatuswhile, at the same time, speeding up said positioning in the mannerdescribed above. In this regard, it is proposed to increase the accuracyby eliminatting the necessity of calculating deviations in wire lineelasticity, to a maximum extent. In this way, the possibili'ty of humanerror is measurably reduced.

A further object is to promote speed and accuracy in positioning a toolat a predetermined depth, through the provision of a regular spacing ofthe markers in an arrangement that includes main markers that areuniformly spaced along the length of the well, in association withauxiliary markers, regularly spaced apart in the intervals occurringbetween adjacent main markers. In this way, it is proposed, in effect,to calibrate, so to speak, an oil well over its entire depth, in muchthe same way as one would calibrate a. rule with main indicia and withsubindicia that represent fractional distances between adjacent mainmarkings or gradations.

Another object is to so design the marker as to permitinterchangeab-ility of component parts thereof, as between the main andauxiliary marking devices. rIlhus, a retaining sleeve and `a pair oflocking rings embodied in the invention may be common to both the mainand auxiliary marking devices, in `accordance with the invention, thusto lower the over-all cost of manufacture while, at the same time,simplifying assembly of the marking devices.

A further object is to permit incorporation of the invention in aconventional casing coupling, if desired.

Other objects will appear from the following description, the claimsappended thereto, and from the annexed drawing, in which like referencecharacters designate like parts through the several views, and wherein:

FIGURE l is a side elevational view of one of the auxiliary markingdevices formed according to the present invention, a casing section towhich the same is applied being shown fr-agmentarily, in dotted lines;

FIGURE 2 is an end view of the retaining sleeve embodied in the markingdevice, as seen from the line 2-2 of FIGURE l;

FIGURE 3 is an end view of the marking device shown in FIGURE l;

FIGURE 4 is a transverse sectional view substantially on line `4-4 ofFIGURE l;

FIGURE 5 is a longitudinal sectional view substantially on line 5 5 ofFIGURE 2;

FIGURE 5a is a view like FIGURE 5, showing a main marker;

FIGURE 6 is a diagrammatic representation of an oil well, illustratingthe various formations or strata penetrated thereby, in relation to`conventional well casing components;

FIGURE 7 is a diagrammatic representation, illustrating a through casingcorrelation -log including correlation curves and a conventional collarlog, in connection with the well diagrammatically shown in FIGURE 6;

FIGURE 8 is a view like FIGURE 6, showing in a diagrammatic fashionauxiliary and main marking devices attached to the casing in accordancelwith the present invention;

FIGURE 9 is a correlation log according to the present invention, havingthe positions of the aux-iliary and main marking devices graphicallydelineated thereon;

FIGURE 10 is a diagrammatic showing of the well illustrtaed in FIGURE 6,showing a fragmentary portion of said well on a scale slightly enlargedabove that of FIGURE 6, and illustrating a collar locator and associatedperforating device, said locator and perforating device being shown indilerent dotted line positions to which the same may be lowered; and

FIGURE 1l is a view like FIGURE 10, showing the lower portion of thewell illustrated in FIGURE 6, and illustrating a conventional loggingtool and collar-locator in use during the logging of a well, the casingof which is equipped with marking devices according to the presentinvention.

Referring to the drawing in detail, I have shown, in FIGURES 1-5, oneform of marking device adapted for carrying out the invention. In thisform of the invention, which constitutes a presently preferredembodiment, I provide an elongated casing marker applicable to aconventional oil well casing or pipe generally designated 10.

The marker shown in FIGURES 1-5 has been generally designated 12, andincludes an elongated retaining sleeve 14 the outer diameter of which isslightly less than half the length thereof, the inner diameter lof thesleeve being slightly greater than the diameter of the well casing, soas to permit the sleeve to be slidable upon the well casing to aselected location.

As shown to particular advantage in FIGURES 4 and 5, I provide, midwaybetween the opposite extremities of the retaining sleeve 14, a pair ofdiametrically opposed, transversely curved recesses 16, each of which iscurved through approximately 90 degrees of the inner circumference ofthe retaining sleeve. The recesses 16 are comparatively shallow, so.that the retaining sleeve remains of appreciable thickness and strengthat the location of the recesses. The recesses are concentric with oneanother and with the retaining sleeve, and each recess has straight sidewalls 18 intersecting perpendicularly with end walls 20, correspondingend walls of the recesses being aligned transversely of the retainingsleeve, on a line perpendicular to the axis of said sleeve.

In the illustrated, presently preferred embodiment, I formdiam'etrically opposed radial openings 22 in the retaining sleeve,`communicating between the outer surface of the sleeve and the recesses.The openings communicate with the recesses at the center point of therecesses, whereby to be disposed in registration with threaded sockets27 formed in the convex outer surfaces of transversely curved insertplates 24. Plates 24 are formed complementarily to the recesses, so asto ll the recesses in the manner shown in FIGURE 4. The plates, thus,have concave inner surfaces ilush with the wall 2S of the bore of thesleeve.

Designated at 26 are screws or equivalent threaded fastener members,extending through the openings 22 so as to be threadedly engaged in thesockets 27. In this way, the insert plates or elements 24 are xedlysecured in position, within their associated recesses 16. The screws, attheir outer ends, do not project beyond the outer circumference of theretaining sleeve, in the illustrated, preferred embodiment.

At 28 I provide a pair of identical, oppositely arranged locking orclamping collars, abutting against the opposite ends of the retaining orsupport sleeve 14, in the installed position of the marker 12.

The collars 28 are respectively `formed with arcuate collar members 29,the maximum diameters of which are no greater than the outer diameter ofthe sleeve 14, when the collar members 29 are secured 1in position aboutthe casing. The collar mem-bers are adapted to be radially contractedinto gripping engagement with the casing, thus to hold the sleeve 14against endwise movement from its assigned position.

For the purpose of contracting the collar members, there are providedstuds 30 each of which is formed, at its opposite ends, with threads ofopposite hand. Wrenchreceiving enlargements or collars 32 are providedupon the studs, intermediate their ends, so as to facilita-te treadingof the studs into or out of confronting, oppositelythreaded recesses 31formed in the ends of the collar member.

Thu-s, it will be readily seen that in applying the device to thecasing, one merely slips a collar 28 onto the casing section, beforesaid casing section is run into the bore hole. Then, the sleeve 14 issimilarly applied to the casing section, and is slidably adjusted to theselected point at which it is to be secured imm-ovably to the casingsection. The other collar 28 is now applied, after which the collars, inabutting relation to the sleeve 14, are radially contracted, so as topermanently secure the sleeve to the casing, with the elements 24 indirect contact with the surface of the well casing.

A marking device such as shown in FIGURES 1 5 can appropriately ibeconsidered as an auxiliary marker, containing a single pair ofdiametrically opposed plates or elements 24. The plates or elementswould be formed of a material that is designed to produce a reaction ina sensing or detecting instrument, such as a conventional collarloca-tor. The material used for the elements 24 would be selectedaccording to `the type of collar locator or other logging tool that isto be employed.

Thus, it may be noted that many collar locators in use today work on theprinciple of a magnetic field. In this event, the elements 24 might -bepermanent magnets. As

the collar locator moves to a position abreast of the elements 24 of amarker 12, a reaction would `be produced at the surface, translated intoa deviation upon a correlation curve disposed adjacent a log on whichthe positions of the markers are charted.

In other instances, the elements 24 might be of a radioactive material,used with a logging tool that reacts by accentuating the characteristiccurves on a gamma-ray neutron log. Then, too, the elements `could be oflead, s'o as to tend to reduce or shield completely the signal from agamma-ray neutron logging tool. Other materials might be employed, aslong as they will produce a reaction at ground level when a suitablesensing instrument or logging tool is lowered into the casing past themarkers.

At periodic intervals along the length of the casing, there maybelocated what might appropriately -be termed a main marker, such as oneshown by way of example in FIGURE 5a. This marker would be one thatwould produce a different type of reaction at .the ground surface, fromthat produced `by the markers having only one type of element 24, suchas shown in FIGURES 1-5. In FIGURE 5a, the marker has been generallydesignated 12a, and includes a support sleeve 14a, having diametricallyopposed recesses 16a, exactly as in the iirst form of the invention. Inthis form of the invention, there could tbe mounted in each recess aplurality of elements 24a, 2411, 24C. Elements 24a might be of the samematerial as the elements 24. This would also be true of elements 24C.Elements 2411, however, might be of a different material, so as toproduce a different reaction at the ground level. Assuming, for example,that elements 24, 24a, and 24e are of permanent magnet material, theelements 24h might be `of a radio-active material, and the logging toollowered into the bore hole could be prepared in such a way as to have asub-assembly reacting to permanent magnets, and another sub-assemblyreacting to radioactive material. In this way, at the -ground levelthere would lbe logged a plurality of regularly spaced auxiliarymarkers, after which there would appear on the log a main gradation,followed by a plurality of the subordinate or auxiliary gradations, etc.

Alternatively, a main marking means could comprise merely a plurality ofthe markers shown in FIGURE 1, disposed in end-to-end, abuttingrelation. One might employ, `for example, two sleeves 14 disposed inendabutting relation, with collars 28 lbeing disposed at opposite endsof the pair of sleeves. In this way, only one material need be used forthe elements 24,` requiring in turn only one type of sensing instrumentor logging tool.

In any event, itis mainly important to note at this time that theinvention embraces the concept of main markers used to designate mainreference or datum points, together with auxiliary markers used todesignate subordinate datum points. One could lower a tool directly to amain marker, and using this as a datum point, could then raise or lowerthe tool to a selected auxiliary marker, using this as an auxiliaryreference point, thereafter moving the apparatus to the selectedposition.

It may also be noted that by reason of the construction illustrated anddescribed, main or auxiliary :markers could be assembled directly on thesite, as necessary, during the lowering of the casing into the borehole. A selected type of marker can be assembled, slid onto the nextcasing section that is to be coupled, secured in place at the prescribedlocation along the length of said section, and thereafter, the casingsection may be coupled to the next ylower section, and lowered in-to thehole. Further, the arrangement permits interchangeability of componentsofthe dev-ice, so that a sleeve such as shown Iat 14a can be used toreceive either a plurality of elements in the manner shown in FIGURE 5a,`or alternatively, can be used to receive a single element such as shownin FIGURE 5 at 24.

In FIGURE 6, a typical well has been shown diagrammatically. In theillustrated example, the welll bore penetrates numerous formations,-designated A through K. By

way of example, two portions of the well are shown. The upper portionrepresents a section extending from formation A to lformation E, fromapproximately 7900 `feet to approximately 8200 feet. The lower sectioncovers formations F through K, and extends from approximately 10,000feet to approximately 10,400 feet. The Well casing 10 is illustrateddiagram-matically, as being composed of a plurality of casing sections34 each of which covers a distance of 331/3 feet. The sections arejoined together by casing collars or couplings 36 of conventionalconstruction. At approximately 10,290 feet, the casing is Iprovided witha tloat shoe 40. This is on the lower extremity of the casing, anddisposed approximately l or l5 feet thereabove -is a oat collar 38. Thewell bore has been designated at 42, and the open space below 10,290feet represents an open hole or uncased section 44.

In FIGURE 7, there is shown a conventional through casing correlationlog, for the well shown in FIGURE 6. The correlation log includes firstand second correlation curves 46, 48, derived from the use ofconventional logging tools, Iwhich are lowered into the bore 42 fully tothe bottom thereof to produce reactions as said tools pass the severalformations A through K. The nature of the formations is such as to causethe logging tools to res-pond thereto, with the response beingtransmitted to the surface and being translated into a graphicrepresentation on the log, as shown at 46, 48, respectively.

Between the correlation curves 46, 48, there is illustrated a collar log50. This has the various well levels marked thereon, in gradati'ons of100 `feet each. Through the use of collar locators, the log is providedwith markings 52, at intervals of 331/3 feet, indicating the positionsof the casing collars 36.

Heretofore, the general practice has been to use a correlation log `suchas sho-wn in FIGURE 7. However, inaccuracies have been produced, as wellas the loss of time due to the fact that in wire line operations, it hasbeen necessary to lower the apparatus fully to the bottom, to check thewire line accuracy. Further, it is often difficult to identify aparticular collar.

In FIGURE 8, there is diagrammatically shown a well, the casing lofwhich is provided not only with the conventional casing section-s 34 andcasing collars 36, but also, with auxiliary and main markers 12, 12a,respectively, according to the present invention.

It will be seen that by way of example, I have attached an auxiliarymarker 12, of the type shown in FIGURES 1-5, to the casing at a depth of8,050 feet. Another one of the markers 12 is attached to the lower endof the casing, immediately below the float shoe 40, at approximately10,29() rfeet. A main or composite marker 12a is attached at 10,150feet. The middle element 24h of the marker 12a can be considered as acenter marking element, said 4middle element bei-ng flanked by elements24a, 24C.

In the illustrated arrangement, the marking elements are selected insuch a way that the element of the marking device 12, shown abreast offormation B in FIGURE 8, would primarily aifect the collar log 50, atthe mentioned depth of approximately 8,050 feet indicated on said log.Referring to FIGURE 9, a rst auxiliary marking S4 would thus be placedupon said collar log.

At approximately 10,150 feet, as previously noted, there would be threemarking elements, in the main marking device 12a. The upper element 24ain this group is of a material similar to that used in the marker 12,and thus primarily affects the collar log 50 so as to produce a marking58. The middle element 24b in this group is of a material that producesa different response at the ground surface, and that primarily ailectsthe correlation curves 46, 48, as shown at 62, 64, respectively inFIGURE 9.

The element 24C, in the marker 12a, being of the same material as theelements 24, 24a, would primarily affect the collar log 50 to produce amarking 60, the markings 58, 60 of the collar log being disposed inanking relation to the deviations or pronounced indentations 62, 64produced in the correlation curves 46, 48 respectively.

The lower marker 12 contains an element 24, and, therefore, primarilyaiects the collar log 50 to produce marking 56.

Other arrangements can -obviously be employed. One could producemarkings on the colla-r log, at regular intervals over the full lengthof the same, which intervals might be greater than the intervals betweenadjacent casing collar markings 52. Then, rnain markings could beproduced both on the collar l-og and on the correlation curves, as shownat 58, 60, 62, 64, through the use of the main marking devices 12a.

Referring now to FIGURE l0, there is here shown a typical employment ofthe method and means constituting the present invention. A conventionalperforating device generally designated 66 i-s provided with perforatingjets, bullets, or the like, as at 68. Said device is lowered into thecasing by means of a wire line or suspension cable 70, which is designedto constitute a combination transmitting, conductor, and hoisting cable.At 72 I have generally designated a collar and/ or marker locator. This,like the perforating tool 66, is of conventional design.

Of course, the perforating gun is merely exemplary of one type ofapparatus that might be lowered into the well casing along with thecollar locator or other logging tool 72.

The upper dotted line showing of the tools 72, 66, represents theapproximate positions thereof when correlating or recording the reactionto the upper casing marker 12. The collar locator 72, in thesecircumstances, is directly abreast 4of said upper marker 12.

In these circumstances, through a lead 74 extending from the collarlocator to` the yground surface, there is produced a reaction in apotential difference indicator 78, connected in series with recordingand ground 82. 'Ihe upper marker 12 thus serves as a ydatum or referencepoint, to check the wire line accuracy. The attached collar locator 72and perforating device 66 are now lowered to the lower dotted lineposition in FIGURE 10. This is 'done without loss of time, due to theuse of the marker 12 as a datum point for checking the accuracy of thewire line. No necessity of lowering the equipment to the bottom Iof thewell exists. On movement of the perfo-rating device to the exactposition desired, abreast `of a producing formation D, the projectilescarried thereby are tired, by closure of a switch 86 which is normballyyopen in a lead 76 extending from the perforating device. A source ofpower 84 is provided in this circuit, having one terminal connected toground as at 88.

Referring now to FIGURE 1l, there is here shown the lower portion of thewell bore. By way of example, I have illustrated a collar locator 72secured to a logging device 90. The logging device is located abreast ofthe marker 12a. The middle marker element 24h of the marking device 12acontains radioactive material, and a response is produced in the loggingtool, which is graphically translated into deviations such as shown at62, 64, in FIGURE 9.

The normal procedure during logging operations is to lower the loggingtool 90 fully to the bottom of the well or the deepest depth to belogged. Then, the well is logged as the tool is moved upwardly out ofthe hole.

However, as the tool is being lowered into the hole, periodic checks andcorrections must be made to compensate for deviations such as stretch,weight, temperature, etc., in the transmitting, conducting, and hoistingcable 70.

When a well having casing markers attached to the casing string inaccordance with the invention is to be logged, a log similar to thatshown in FIGURE 9 should be obtained. As the collar locator, with thelogging tool 90 attached, moves upwardly, the collar locator willproduce the deviations or markings 56, 60, 58, and 54, due to the factthat the collar locator in this instance is sensitive to magneticmaterial, with the elements 24, 24a and 24C being of permanent magnetmaterial. The logging tool, meanwhile, is sensitive to radioactivematerial, and thereby produces the deviations 62, 64, as it passes theelement 24b.

This will complete preparation of the log shown in FIGURE 9, and saidlog is thereafter available during any operations to be performed in thewell, whether they be perforation operations or some other type of wireline activities. For that matter, the invention is usable to equaladvantage when operations other than those involving wire lines arebeing carried out.

One example of the use of the device, after completion of the log, isshown in FIGURE l and has previously been described herein.

It will be understood that the casing markers could be used in liners aswell as on casing strings. Accordingly, the reference to a well casingis to be considered as embracing liners. Liners, in the nal analysis,are merely smaller strings of casing which are run or positioned inopen-hole sections after the regular casing string has been inserted.Said open-hole section might be drilled after the regular casing stringhas been placed in the well bore. The liner is then lowered, through thecasing string previously inserted, into the open-hole section.

It will be further noted that the device could be made as part of aconventional casing coupling. In this type of arrangement, theprinciples of the invention as abovenoted would be retained, but thedevice would be threaded and actually run as part of the casing string.

It is believed apparent that the invention is not necessarily confinedto the specific use or uses thereof described above, since it may beutilized for any purpose to which it may be suited. Nor is the inventionto be necessarily limited to the specific construction illustrated anddescribed, since such construction is only intended to be illustrativeof the principles of operation and the means presently devised to carryout said principles, it being considered that the invention comprehendsany changes in construction that may be permitted within the scope ofthe appended claims.

What is claimed is:

l. In a device for speeding the positioning of apparatus in a wellcasing at a desired depth, and for promoting accuracy in saidpositioning, an improved casing marker for use in association with asensing instrument capable of being lowered into said casing,comprising: arcuately curved marker means for producing in a sensinginstrument a response recordable at ground level when said instrument islowered into a well casing in juxtaposition to said means; a support forsaid means shaped as -a sleeve proportioned to encircle a well casing,and formed with an inwardly -facing recess complementing and receivingsaid means with said means substantially liush with the inner |bore ofthe sleeve; and means for mounting the sleeve on an imperforate portionof the casing at any of a plurality of selected locations along thelength of the casing.

2. In a device for speeding the positioning of apparatus in a wellcasing at a desired depth, and for promoting accuracy in saidpositioning, an improved casing marker for use in association with asensing instrument capable of being lowered into said casing,comprising: arcuately curved marker means for producing in a sensinginstrument a response recordable at ground level when said instrument islowered into a well casing in juxtaposition to said means; a support forsaid means shaped as a sleeve proportioned to encircle a well casing,and formed with an inwardly facing recess complementing and receivingsaid means with said means substantially flush with the inner bore ofthe sleeve; and clamping collars extendible about said casing andclampingly engageable therewith and disposed at opposite ends of saidsupport so as to j casing, said collars being adapted for mounting thesupport on an imperforate portion of the casing at any of a plurality ofselected locations along the length of the casing.

3. In a device for speeding the positioning of apparatus in a wellcasing at a desired depth, and for promoting accuracy in saidpositioning, an improved casing marker for use in association with asensing instrument capable of being lowered into said casing,comprising: a plurality of concentrically curved, angularly spacedmarker elements adapted for producing in a sensing instrument a responserecordable at ground level when said instrument is lowered into a wellcasing in juxtaposition to said elements; a support for said elementsshaped as a sleeve concentric with said elements, said sleeve beingproportioned to encircle a well casing and being formed with internalrecesses complementing and receiving said elements; and clamping collarsextendible about said casing and clampingly engageable therewith anddisposed at opposite ends of the support so as to constitute abutmentslimiting the support against movement from a selected location along thelength of the casing, said collars being adapted for mounting thesupport upon an imperforate portion of the casing at any of a pluralityof selected locations along the length of the casing.

4. In a device for speeding the positioning of apparatus in a wellcasing at a desired depth, and for promoting accuracy in saidpositioning, an improved casing marker for use in association with asensing instrument capable of being lowered into said casing,comprising: at least two diametrically opposed, concentrically curvedmarker elements adapted for producing in a sensing instrument a responserecordable at ground level, when said instrument is lowered into a wellcasing in juxtaposition to said elements; a support for said elementsshaped as a sleeve concentric with the respective elements, said sleevebeing proportioned to encircle a well casing and being formedintermediate its ends with diametrically opposed, internal recessescomplementing and receiving the respective elements, said elementshaving confronting, arcuately concave, inner faces flush with the innersurface of the sleeve when the elements are engeged in the respectiverecesses; and clamping collars extendible about said casing andclampingly engageable therewith and disposed at opposite ends of thesupport so as to constitute abutments limiting the support againstmovement from a selected location along the length of the casing, saidcollars being adapted for mounting the support upon an imperforateportion of the casing at any of a plurality of selected locations alongthe length of the casing.

5. In a device for speeding the positioning of apparatus in a wellcasing at a desired depth, and for promoting accuracy in saidpositioning, an improved casing marker for use in association with asensing instrument capable of being lowered into said casing,comprising: at least two diametrically opposed, concentrically curvedmarker elements adapted for producing, iu a sensing instrument, aresponse recordable at ground level when said instrument is lowered intoa well casing in juxtaposition to said elements, said elements havingarcuately convex outer faces formed with threaded sockets; a supportsleeve for said elements concentric with the respective elements, saidsleeve being proportioned to encircle a well casing and being formedintermediate its ends with diametrically opposed, internal recessescomplementing and receiving the respective elements, said elementshaving confronting, arcuately concave, inner faces flush with the innersurface of the sleeve when the elements are engaged in the respectiverecesses, the sleeve having radial openings aligned with the respectivesockets and communicating between the recesses and the outer surface ofthe sleeve; threaded fastener members extending through said openingsand engaged in the sockets to connect said elements to the sleeve; andclamping collars extendible about said casing and clampingly engageableaccuracy in said positioning, an improved casing marker for use inassociation with a sensing instrument capable of being lowered into saidcasing, comprising: at least two diametrically opposed, concentricallycurved marker elements adapted for producing, in a sensing instrument, aresponse recordable at ground level when said instrument is lowered intoa well casing in juxtaposition to said elements, said elements havingarcuately convex outer faces formed with threaded sockets; a supportsleeve for said elements concentric with the respective elements, saidsleeve being proportioned to encircle a well casing and being formedintermediate its ends with diametrically opposed, internal recessescomplementing and receiving the respective elements, said elementshaving confronting, arcuately concave, inner faces flush with the innersurface of the sleeve when the elements are engaged in the respectiverecesses, the sleeve having radial openings aligned with the respectivesockets and communicat-V ing between the recesses and the outer surfacesof the sleeve; threaded fastener members extending through said openingsand engaged in the sockets to connect said elements to the sleeve; andclamping collars extendible about said casing and clampingly engageabletherewith and disposed at opposite ends'of the sleeve so as toconstitute abutments limiting the sleeve against movement from aselected location along the length of the casing, each of said collarsincluding a radially contractible, arcuate collar member having spacedends formed with oppositely threaded recesses, each collar furtherincluding a stud having threads .of opposite hand at its respectiveends, said studs being engaged in the lastnamed recesses for contractingthe collar member to the well casing responsive to rotation of thestuds, thus to mount the'sleeve upon an imperforate portion of thecasing at any of a plurality of selected locations along the length ofthe casing, said fastener members and studs being disposed whollyinteriorly of the outer circumferences of the sleeve and collar members.

References Cited in the le of this patent Marquis et al L..-" Feb. 14,1956

1. IN A DEVICE FOR SPEEDING THE POSITIONING OF APPARATUS IN A WELLCASING AT A DESIRED DEPTH, AND FOR PROMOTING ACCURACY IN SAIDPOSITIONING, AN IMPROVED CASING MARKER FOR USE IN ASSOCIATION WITH ASENSING INSTRUMENT CAPABLE OF BEING LOWERED INTO SAID CASING,COMPRISING: ARCUATELY CURVED MARKER MEANS FOR PRODUCING IN A SENSINGINSTRUMENT A RESPONSE RECORDABLE AT GROUND LEVEL WHEN SAID INSTRUMENT ISLOWERED INTO A WELL CASING IN JUXTAPOSITION TO SAID MEANS; A SUPPORT FORSAID MEANS SHAPED AS A SLEEVE PROPORTIONED TO ENCIRCLE A WELL CASING,AND FORMED WITH AN INWARDLY FACING RECESS COMPLEMENTING AND RECEIVINGSAID MEANS WITH SAID MEANS SUBSTANTIALLY FLUSH WITH THE INNER BORE OFTHE SLEEVE; AND MEANS FOR MOUNTING THE SLEEVE ON AN IMPERFORATE PORTIONOF THE CASING AT ANY OF A PLURALITY OF SELECTED LOCATIONS ALONG THELENGTH OF THE CASING.